Post-cessation weight gain (PCWG) can deter a quit attempt, precipitate smoking relapse, and contribute to health issues related to excess body weight. The majority of weight gain occurs within 3-6 months of quitting smoking, with weight gains averaging 9.3 pounds (5-30 pound range). PCWG has been attributed primarily to increased caloric intake due to between-meal snacking on foods high in fat and sugar. Two decades of treatment research to prevent PCWG has yielded modest success at best. The importance of identifying efficacious treatments for the prevention of PCWG is highlighted by research showing that 70 percent of treatment- seeking smokers are overweight or obese; they gain the most weight upon quitting smoking, and are least accepting of PCWG. Novel theory-driven behavioral interventions that consider the mechanisms that underlie post-cessation increases in food intake may reduce PCWG and promote smoking abstinence. To advance the science and practice of interventions to reduce PCWG, we propose to target reward-related mechanisms common to smoking and palatable food intake. Through a novel application of a behavioral activation intervention to smoking cessation and to post-cessation weight gain (BAS+), we will increase opportunities for reinforcement and enhance the pleasure obtained from these reinforcers. The efficacy of BAS+ plus transdermal nicotine (TN) vs. Standard Smoking Cessation Counseling (SC) plus TN will be evaluated in a randomized clinical trial of 426 treatment seeking smokers (ages 18-65). Participants will receive 8 BAS+ or SC sessions plus TN over a 10-week period. The primary outcomes will be PCWG and biochemically verified point prevalence smoking abstinence 26-weeks after the target quit date. Food intake (secondary outcome) will be measured via 24-hour food recall conducted over 3 consecutive days at pre- treatment, mid-treatment, end of treatment, and follow-up. Mechanisms by which BAS+ reduces PCWG and promotes smoking cessation (e.g., alternative reinforcers, relative reinforcing value of food, food reward, and food cue-induced craving) will be assessed prior to, during and at the end of treatment (week 8). Moderators will be assessed pre-treatment (e.g., gender, depression symptoms, and weight concerns). The proposed study breaks new conceptual and empirical ground by: (1) providing the first evaluation of the efficacy of BAS+ for smoking cessation and PCWG as an adjunct to the most widely used pharmacotherapy for smoking cessation; (2) examining the mechanisms by which BAS+ reduces food intake and weight gain; and (3) identifying whether individual differences that may impact intervention efficacy. If the hypotheses are supported, the findings would suggest that targeting reward-related mechanisms common to both smoking and eating is: (1) an effective approach to promoting smoking cessation, while minimizing PCWG; and (2) is a viable approach for addressing two rewarding behaviors concurrently, without risking compensatory increases in one of those behaviors.